| This work defines and characterizes a novel analytical technique known as infrared atmospheric pressure matrix-assisted laser desorption/ionization (IR AP-MALDI) ion trap mass spectrometry. This configuration, combining AP-MALDI with an ion trap mass spectrometer, was developed in the Cotter lab, and that initial design has been modified to include an infrared laser in addition to the typical ultraviolet laser normally utilized for MALDI analysis. AP-MALDI is a variation on vacuum MALDI in that the source region is at atmospheric pressure. This configuration allows for collisional cooling of ions before they enter the mass analyzer, resulting in soft ionization. AP-MALDI affords facile coupling to a quadrupole ion trap mass spectrometer which can provide MS/MS and MSn capabilities. The recent addition of an infrared laser encourages the use of aqueous samples since the 2940 nm wavelength is near the stretching frequency of the O-H bond. Consequently, water and glycerol can be used as matrix compounds and samples can be analyzed in liquid form.; The focus of this research has been to exploit IR AP-MALDI for the analysis of oligosaccharides and their complexes, both with other carbohydrates and with proteins, with the use of aqueous physiological matrixes. Carbohydrates play many key biological roles, yet mass spectrometric studies of their structure and function remain limited. IR AP-MALDI has become a powerful technique to study the structure of carbohydrates containing labile linkages, including that of sialic acid. Spectra of oligosaccharides containing sialic acid result in primarily molecular ion, with minimal in-source fragmentation. The MS/MS capabilities of the mass spectrometer allow for more complete structural coverage of these carbohydrates, while cation adduction serves to promote alternative fragmentation patterns leading to complementary structural information.; This carbohydrate work has been extended into the study of oligosaccharide-based non-covalent complexes. Infrared AP-MALDI promotes non-covalent complex stabilization and visualization. The study of non-covalent complexes includes both sugar-sugar interactions as well as sugar-peptide interactions. These studies are aimed at determining the residues of importance for carbohydrate-based biological interactions. |
